title: Heparin-induced thrombocytopenia.
abstract: OBJECTIVE
  To highlight the importance of heparin-induced thrombocytopenia (HIT), a potentially fatal adverse effect of heparin therapy.
  
  
  METHODS
  There are two types of HIT with distinct etiology. Type 1 HIT is a relatively mild thrombocytopenia of early onset that generally resolves with ongoing heparin therapy. Clinical complications are uncommon. Type 2 HIT, which is more severe, is the main focus of this report. Five patients receiving heparin therapy developed type 2 HIT, which in some cases resulted in complications that required limb amputation, or eventuated in death.
  
  
  CONCLUSIONS
  In a patient receiving heparin therapy, the development of thrombocytopenia should alert the caregiver to the possible development of HIT. Prompt management of HIT can help prevent complications. HIT usually manifests 5-8 days after starting heparin therapy. The platelet count usually decreases to less than 100 x 10(3)/mm3. It generally normalizes within 5-7 days after discontinuing heparin therapy. In spite of the thrombocytopenia, thrombosis or disseminated intravascular coagulation can occur. The management may be subdivided into three clinical situations: mild-to-moderate asymptomatic thrombocytopenia, severe thrombocytopenia with a platelet count of less than 50 x 10(3)/mm3, and thrombosis or embolism complicating HIT.
  
  
  CONCLUSIONS
  Heparin-induced thrombocytopenia is an uncommon but potentially serious, and sometimes lethal, complication of heparin therapy. Therefore, it is important to be aware of the possibility of the development of HIT with heparin therapy, to recognize it early, and to manage it appropriately before the manifestation of adverse effects.
authors.affiliation: Department of Medicine, University of Toronto, Sunnybrook Health Science Center, North York, Ontario, Canada.
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: M J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: D N
authors.initials: DN
authors.lastname: Sauder
mesh_terms: D000328:Adult; D000368:Aged; D000721:Ancrod / Q000627:therapeutic use; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D017809:Fatal Outcome; D005260:Female; D005734:Gangrene; D006493:Heparin / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D012701:Serotonin / Q000097:blood; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000188:drug therapy / Q000473:pathology; D013923:Thromboembolism / Q000139:chemically induced
chemical_list: D000925:Anticoagulants; D012701:Serotonin; D006493:Heparin; D000721:Ancrod